Discovering Pleiotropic Genes Involved in the Motility and Attachment of Burkholderia unamae
Authors:Dro Amirian, Jeanine Asprer, Allison Garcia
- Michelle Lum, Associate Professor of Biology, Loyola Marymount University
- Shelley Thai, Assistant Professor of Biology, Glendale Community College
The Burkholderia sp. has been studied for its role in human diseases. However, various species are non-pathogenic and associate with plants. Burkholderia unamae, in particular, forms symbiotic relationships with plant roots. It promotes plant growth through nitrogen-fixation and ACC (1-aminocyclopropane-1-carboxylic acid) deaminase activity. However, the specific mechanism by which it colonizes plant tissue to exert these effects has yet to be revealed. This study aims to identify genes involved in this process, more specifically, in motility and attachment via exopolysaccharide (EPS) production. Transposon mutagenesis using Tn5-RL27 was used to randomly generate mutations within the B. unamae genome. Motility mutants were screened using the standard motility plate assay while EPS mutants were screened on yeast-extract mannitol agar (YMA) plates. Genomic regions flanking the Tn5-RL27 transposon were then sequenced to identify the disrupted genes. Of the 13 mutants studied, six were observed to both over-produce EPS and be non-motile. The pleiotropy demonstrated by these genes suggests that they play a role in regulating at least one or both phenotypes. One of the disrupted genes was flhD, whose product is responsible for regulating flagellar production in other organisms, while another gene regulates protein hydrolysis. The third mutant contains a disruption in the 23S rRNA region. Various genes appear to be involved in the mechanisms of motility and EPS production. It would be interesting to determine if the overproduction of EPS is due to a compensatory reaction to the absence of or decrease in motility. Further studies are required to elucidate this phenomenon and to determine how this may affect the ability of B. unamae to colonize plant tissue.